growers@sgcotton.com.au Roger Tomkins - Greenmount Press

Evaluation of insecticides for
controlling pale cotton stainer bug
■ Moazzem Khan and Kristy Byers, DAFF Queensland
WITH the increased adoption of Bollgard II cotton in
recent years, higher levels of pale cotton stainer (PCS)
infestations have been reported from different areas.
PCS cause damage to bolls by inserting their long proboscis
to feed on developing and mature seeds. This feeding activity
causes black spots on the boll, warty growths inside the boll wall
and brown coloured lint. Feeding on seeds results in tight lock,
preventing the lint from fluffing out as the boll opens.
In Australia there are no insecticides registered for the control
of PCS and they are often incidentally controlled by broadspectrum
insecticides such as synthetic pyrethroids, carbamates
and organophosphates that target other pests. As an occasional
pest, PCS received very little attention with regard to insecticide
evaluation. To date, only one trial has been conducted to identify
effective insecticides for PCS (see The Australian Cottongrower
29(2) 2008, pages 41–42). But it is essential to identify which
insecticides are effective against this pest whilst also compatible
with existing IPM.
In cotton, PCS infestation occurs late in the season when large
numbers of whitefly and aphids are also common. Therefore
insecticides that are effective against PCS, as well as whitefly
and aphids are highly sought after. Pegasus is recommended for
both whitefly and aphids (see Cotton Pest Management Guide
2011–12) and was therefore used in this trial to test its efficacy
against PCS.
The broad aim of this study was to identify insecticides that
were effective against PCS.
TABLE 1: Insecticides used in the trial
Treatment Formulation (g/L) Rate (mL/ha)
Pegasus 400 Diafenthiuron 500 SC 400
Pegasus 800 Diafenthiuron 500 SC 800
Pegasus 400+salt Diafenthiuron 500 SC 400 + 10 g/L of
+ NaCl
water
Shield 125 Clothianidin 200 SC 125
Shield 250 Clothianidin 200 SC 250
Shield 125+salt Clothianidin 200 SC + 125 + 10 g/L of
NaCl
water
Danadim 300 Dimethoate 400 EC 300
Danadim 500 Dimethoate 400 EC 500
Danadim 300+salt Dimethoate 400 EC + 300 + 10 g/L of
NaCl
water
Control Untreated —
Trial
The trial was conducted at the late boll stage of Bollgard II
cotton (variety Sicot 71BRF) at the Kingaroy Research Station. The
trial comprised 10 treatments, each with three replications in a
randomised block design. Treatment details are given in Table 1.
Trial plots were five rows wide by 15 metres long. There was a
buffer row between each replication to facilitate spray equipment
and to minimise insecticide drift between plots. The insecticides
FIGuRE 1: Per cent corrected mortality to PCS for different treatments trialled in Bollgard II cotton
August–September 2012 The Australian Cottongrower — 55